Factors affecting high cumulative radiation exposure from paediatric computed tomography

Introduction
To estimate occurrence rate of high cumulative radiation exposure from paediatric computed tomography (CT), and to determine influential factors on high-dose inclination.

Material and methods
Patients below 18 years old receiving at least 50 mSv of a cumulative dose during a 5-year period in a tertiary care centre were retrospectively enrolled. Individual patient characteristics, diagnoses, frequency of exa­minations, scanner sites, designated scans, and effective doses were recorded. Collective doses were compared among groups of the diagnoses and scanner sites, and regression analyses were applied.

Results
Of 2771 patients, 3.2% received individual cumulative doses between 50 and 303 mSv (median, 74 mSv). Frequency of examinations ranged from 1 to 13 times (median, 4 times) per patient. About 70% of the patients had oncological illness. Radiation was predominantly high in a CT simulator that could contribute the percentage of collective dose to twice that of examinations owing to higher scanning parts and CT dose index. Some scanner sites used higher acquisition phases. Regression analysis showed that the number of scanning parts and phases significantly influenced the cumulative dose inclination (p < 0.05) while frequent examinations did not.

Conclusions
There was a low occurrence of paediatrics with high dose accumulation. Significant factors affecting potentially high exposure were customized CT protocols in the specific scanners.